Return exit code 15 (SIGTERM) after SIGTERM. (#551)
Return exit code 15 (SIGTERM) after SIGTERM. (#551)

* Return exit code 15 (SIGTERM) after SIGTERM.
When marian receives signal SIGTERM and exits gracefully (save model & exit),
it should then exit with a non-zero exit code, to signal to any parent process
that it did not exit "naturally".

* Added explanatory comment about exiting marian_train with non-zero status after SIGTERM.

emjotde/amunmt,emjotde/amunn,marian-nmt/marian-train,emjotde/amunn,emjotde/amunmt,marian-nmt/marian-train,emjotde/amunn,emjotde/Marian,marian-nmt/marian-train,marian-nmt/marian-train,emjotde/Marian,emjotde/amunmt,emjotde/amunmt,emjotde/amunn,marian-nmt/marian-train